Question 1

1. Consider a cross-sectional diagram of a microsporangium. You observe four distinct wall layers. The innermost layer consists of cells with dense cytoplasm and often more than one nucleus. What is the primary function of this layer?

A) Protection of the developing microsporesB) Dehiscence of the anther to release pollenC) Nourishment of the developing pollen grainsD) Formation of the hard outer exine

Answer

✓ Correct Answer: Option C

Explanation: The innermost layer is the **Tapetum**. It is characterized by dense cytoplasm and multinucleate cells. Its critical role is to provide nutrition to the developing microspores/pollen grains. The other layers (Epidermis, Endothecium, Middle layers) are mainly protective or aid in dehiscence.

Question 2

2. In a diagram of a mature pollen grain, there is a large irregularly shaped nucleus in one cell and a spindle-shaped cell floating in its cytoplasm. If the large cell is the Vegetative cell, what is the chromosomal status of the smaller cell?

Question 3

3. Imagine a 7-celled, 8-nucleate embryo sac. At the micropylar end, you see a group of three cells. Two of these have prominent finger-like projections at their base called the filiform apparatus. What are these two cells?

A) SynergidsB) AntipodalsC) Polar nucleiD) Egg cell

Answer

✓ Correct Answer: Option A

Explanation: The egg apparatus at the micropylar end consists of two **synergids** and one egg cell. The filiform apparatus is a specialized structure in synergids that guides the pollen tube into the embryo sac.

Question 4

4. A scientist observes Double Fertilization in a flowering plant. If the somatic cell of this plant has 24 chromosomes, how many chromosomes will be found in the Primary Endosperm Nucleus (PEN)?

A) 12B) 24C) 48D) 36

Answer

✓ Correct Answer: Option D

Explanation: Somatic cell 2n = 24, so n = 12. The PEN is formed by Triple Fusion (one male gamete + two polar nuclei), making it triploid (3n). $$PEN = 3n = 3 \times 12 = 36$$.

Question 5

5. In a botanical illustration of a pea seed, you identify the hilum. What does this specific point represent?

A) The opening through which the pollen tube enteredB) The scar where the seed was attached to the stalk (funiculus)C) The region where the embryo is attached to the cotyledonsD) The protective covering of the radicle

Answer

✓ Correct Answer: Option B

Explanation: The **hilum** is a scar on the seed coat that represents the junction between the seed and the funiculus (the stalk connecting the ovule to the placenta).

Question 6

6. Consider a graph of human menstrual cycle hormones. On Day 14, there is a sharp, massive peak in Hormone X, which triggers the rupture of the Graafian follicle. Identify Hormone X.

A) ProgesteroneB) EstrogenC) Luteinizing Hormone (LH)D) Follicle Stimulating Hormone (FSH)

Answer

✓ Correct Answer: Option C

Explanation: The "LH surge" occurs mid-cycle (around Day 14) and is the primary trigger for ovulation (rupture of the Graafian follicle and release of the ovum).

Question 7

7. In a diagram of the male reproductive system, a coiled tube is seen resting on the posterior surface of each testis. This tube leads into the Vas deferens. What happens to sperm while they are stored here?

A) They gain physiological maturity and motilityB) They undergo the second meiotic divisionC) They are decapacitated by seminal fluidsD) They are fertilized by the secretions of the prostate

Answer

✓ Correct Answer: Option A

Explanation: The tube is the **epididymis**. It serves as a site for sperm maturation, where they acquire the ability to move (motility) and the capacity to fertilize the egg.

Question 8

8. A histology slide of the seminiferous tubule shows large, pyramid-shaped cells interspersed between spermatogenic cells. These cells provide support and secrete 'inhibin'. Identify these cells.

A) Leydig cellsB) Interstitial cellsC) SpermatogoniaD) Sertoli cells

Answer

✓ Correct Answer: Option D

Explanation: **Sertoli cells** (or nurse cells) provide structural support, nourishment to developing sperm, and secrete hormones like inhibin to regulate FSH.

Question 9

9. If you were to trace the path of a sperm cell from the site of production to the external environment, which of the following represents the correct sequence?

A) Testis \rightarrow Vas deferens \rightarrow Epididymis \rightarrow Rete testisB) Seminiferous tubules \rightarrow Rete testis \rightarrow Vasa efferentia \rightarrow Epididymis \rightarrow Vas deferensC) Epididymis \rightarrow Seminiferous tubules \rightarrow Vas deferens \rightarrow UrethraD) Vasa efferentia \rightarrow Rete testis \rightarrow Epididymis \rightarrow Vas deferens

Answer

✓ Correct Answer: Option B

Explanation: The correct sequence of the male accessory ducts is: seminiferous tubules \rightarrow rete testis \rightarrow vasa efferentia \rightarrow epididymis \rightarrow vas deferens \rightarrow ejaculatory duct \rightarrow urethra.

Question 10

10. An electron micrograph of a human sperm shows a high concentration of mitochondria in a specific region. This region provides the energy for tail movement. Where is it located?

A) In the AcrosomeB) In the HeadC) In the Middle pieceD) In the End piece of the tail

Answer

✓ Correct Answer: Option C

Explanation: The **middle piece** of the sperm contains numerous mitochondria, which produce energy in the form of ATP to power the lashing movements of the tail for motility.

Question 11

11. During oogenesis, a diagram shows a cell that has completed Meiosis I and is currently arrested in Metaphase II. This cell is released during ovulation. What is this cell called?

A) Secondary oocyteB) Primary oocyteC) OogoniumD) First polar body

Answer

✓ Correct Answer: Option A

Explanation: The **secondary oocyte** is the result of Meiosis I. It begins Meiosis II but stays arrested in metaphase II until fertilization by a sperm occurs.

Question 12

12. Observe a diagram of the female reproductive tract. Fertilization typically occurs in the junction between which two parts of the fallopian tube?

A) Infundibulum and FimbriaeB) Isthmus and UterusC) Ampulla and IsthmusD) Ampulla and Infundibulum

Answer

✓ Correct Answer: Option C

Explanation: Fertilization in humans takes place at the **ampullary-isthmic junction** of the fallopian tube (oviduct).

Question 13

13. In a schematic of the blastocyst, there is an outer layer of cells and an inner group of cells attached to one side. What is the fate of the outer layer (Trophoblast)?

A) It develops into the embryo properB) It attaches to the endometrium and forms the chorionic villiC) It forms the primary germ layers (Ectoderm, Endoderm)D) It differentiates into the umbilical cord vessels

Answer

✓ Correct Answer: Option B

Explanation: The **trophoblast** is the outer layer of the blastocyst that participates in implantation and later forms the fetal portion of the placenta. The Inner Cell Mass (ICM) gives rise to the embryo.

Question 14

14. A medical chart shows a pregnant woman in her third trimester. Which of the following hormones is secreted specifically by the placenta and is NOT present in non-pregnant women?

A) EstrogenB) ProgesteroneC) LHD) hPL (Human Placental Lactogen)

Answer

✓ Correct Answer: Option D

Explanation: Hormones like **hCG** (human Chorionic Gonadotropin), **hPL** (human Placental Lactogen), and **Relaxin** (later in pregnancy) are produced in women only during pregnancy. Estrogen and Progesterone are present in non-pregnant women as well (via the ovary/corpus luteum).

Question 15

15. In a diagram illustrating the 'Fetal Ejection Reflex', which hormone is released from the maternal posterior pituitary to induce strong uterine contractions?

A) OxytocinB) ProlactinC) EstrogenD) Cortisol

Answer

✓ Correct Answer: Option A

Explanation: **Oxytocin**, often called the "birth hormone," is released from the posterior pituitary in response to signals from the fully developed fetus and placenta, leading to labor contractions.

Question 16

16. Consider a graph of the concentration of milk components over the first few days after birth. The initial milk, yellow in color and rich in IgA antibodies, is called:

A) Mature milkB) Lactose-free milkC) ColostrumD) Transitional milk

Answer

✓ Correct Answer: Option C

Explanation: **Colostrum** is the milk produced during the initial few days of lactation. It is critical for the newborn as it provides passive immunity through IgA antibodies.

Question 17

17. Look at a diagram of a flower like Commelina. It has two types of flowers: one that opens normally (Chasmogamous) and one that never opens (Cleistogamous). What is the guaranteed result in cleistogamous flowers?

A) Cross-pollinationB) Autogamy (Self-pollination)C) GeitonogamyD) Genetic variation

Answer

✓ Correct Answer: Option B

Explanation: **Cleistogamous** flowers do not open at all. Therefore, the pollen grains can only land on the stigma of the same flower, ensuring **autogamy**. This process does not require pollinators but lacks genetic variation.

Question 18

18. In some species of Asteraceae and grasses, seeds are produced without fertilization. This visual mimicry of sexual reproduction is known as:

A) ApomixisB) ParthenocarpyC) PolyembryonyD) Amphimixis

Answer

✓ Correct Answer: Option A

Explanation: **Apomixis** is a form of asexual reproduction that mimics sexual reproduction by producing seeds without fertilization.

Question 19

19. Observe a diagram of an Apple fruit. You notice that the fleshy, edible part is derived from the thalamus rather than the ovary. This classifies the apple as a:

A) True fruitB) Parthenocarpic fruitC) Aggregate fruitD) False fruit

Answer

✓ Correct Answer: Option D

Explanation: Fruits that develop from parts of the flower other than the ovary (like the thalamus in apples and strawberries) are called **false fruits**.

Question 20

20. A student studies a diagram of a Dicot embryo. Between the two cotyledons, there is an embryonal axis. The part of the axis above the level of cotyledons is the:

A) HypocotylB) EpicotylC) RadicleD) Coleoptile

Answer

✓ Correct Answer: Option B

Explanation: The **epicotyl** is the portion of the embryonal axis above the cotyledons, which terminates in the plumule (future shoot). The hypocotyl is the portion below.

Accepted Answer

✓ Correct Answer: Option B

Explanation: The spindle-shaped cell is the **Generative cell**. In Angiosperms, the pollen grain is the male gametophyte. Since it is formed after meiosis (2n \rightarrow n), all its constituent cells, including the vegetative and generative cells, are haploid (n).

Grade 12 Biology Quiz: Sexual Reproduction in Plants & Humans (Set 4)

1. Consider a cross-sectional diagram of a microsporangium. You observe four distinct wall layers. The innermost layer consists of cells with dense cytoplasm and often more than one nucleus. What is the primary function of this layer?

2. In a diagram of a mature pollen grain, there is a large irregularly shaped nucleus in one cell and a spindle-shaped cell floating in its cytoplasm. If the large cell is the Vegetative cell, what is the chromosomal status of the smaller cell?

3. Imagine a 7-celled, 8-nucleate embryo sac. At the micropylar end, you see a group of three cells. Two of these have prominent finger-like projections at their base called the filiform apparatus. What are these two cells?

4. A scientist observes Double Fertilization in a flowering plant. If the somatic cell of this plant has 24 chromosomes, how many chromosomes will be found in the Primary Endosperm Nucleus (PEN)?

5. In a botanical illustration of a pea seed, you identify the hilum. What does this specific point represent?

6. Consider a graph of human menstrual cycle hormones. On Day 14, there is a sharp, massive peak in Hormone X, which triggers the rupture of the Graafian follicle. Identify Hormone X.

7. In a diagram of the male reproductive system, a coiled tube is seen resting on the posterior surface of each testis. This tube leads into the Vas deferens. What happens to sperm while they are stored here?

8. A histology slide of the seminiferous tubule shows large, pyramid-shaped cells interspersed between spermatogenic cells. These cells provide support and secrete 'inhibin'. Identify these cells.

9. If you were to trace the path of a sperm cell from the site of production to the external environment, which of the following represents the correct sequence?

10. An electron micrograph of a human sperm shows a high concentration of mitochondria in a specific region. This region provides the energy for tail movement. Where is it located?

11. During oogenesis, a diagram shows a cell that has completed Meiosis I and is currently arrested in Metaphase II. This cell is released during ovulation. What is this cell called?

12. Observe a diagram of the female reproductive tract. Fertilization typically occurs in the junction between which two parts of the fallopian tube?

13. In a schematic of the blastocyst, there is an outer layer of cells and an inner group of cells attached to one side. What is the fate of the outer layer (Trophoblast)?

14. A medical chart shows a pregnant woman in her third trimester. Which of the following hormones is secreted specifically by the placenta and is NOT present in non-pregnant women?

15. In a diagram illustrating the 'Fetal Ejection Reflex', which hormone is released from the maternal posterior pituitary to induce strong uterine contractions?

16. Consider a graph of the concentration of milk components over the first few days after birth. The initial milk, yellow in color and rich in IgA antibodies, is called:

17. Look at a diagram of a flower like Commelina. It has two types of flowers: one that opens normally (Chasmogamous) and one that never opens (Cleistogamous). What is the guaranteed result in cleistogamous flowers?

18. In some species of Asteraceae and grasses, seeds are produced without fertilization. This visual mimicry of sexual reproduction is known as:

19. Observe a diagram of an Apple fruit. You notice that the fleshy, edible part is derived from the thalamus rather than the ovary. This classifies the apple as a:

20. A student studies a diagram of a Dicot embryo. Between the two cotyledons, there is an embryonal axis. The part of the axis above the level of cotyledons is the: